Apparatus for projecting materials in powder form by means of a concentrated electric arc



:- Feb. 15, 1966 G. MONDAlN-MONVAL ETAL 3,235,700

APPARATUS FOR PROJECTING MATERIALS IN POWDER FORM BY MEANS OF A CONCENTRATED ELECTRIC ARC Filed July 1, 1965 Pisa 3,235,700 APPARATUS FOR PROEECTiNG MATERIALS IN POWDER FORM BY MEANS UP A CONCEN- TRATED ELECTRIC ARC Grard Mondain-Monval and Guy Audric, Paris, France, assignors to LAir Liquide, Soeiete Anonyme pour IEtude et lExploitation des precedes Georges Claude Filed July 1, 1963, Ser. No. 291,851 Claims priority, application France, July 27, 1962, 905,359, Patent 1,336,870 3 Claims. (Cl. 219-46) The present invention relates to the projection of materials in powder form, more especially for obtaining me tallic or refractory coatings on articles of any type, by means of a jet of ionised gas which is brought to very high temperature by an electric arc (plasma) or a blow-pipe flame. Apparatus of this type is already known in which the powder to be projected, suspended in an auxiliary gaseous current, is introduced into the plasma jet or into the flame through a radial conduit of circular section opening into the end portion of the neck of the nozzle through which the said jet escapes, and in fact downstream of the inlet of the nozzle. This method of introducing the powdcr into the column of hot gas or flames requires difiicult adjustments in the injection of the powder in order to obtain a good distribution of the powder grains within this column. In addition, the inlet tube for the powder, which is connected by means of a flange to the radial conduit opening into the neck of the column, is considerably overheated.

The apparatus forming the subject of the present invention enables these disadvantages to be overcome; it is characterized in that the powder supply conduit extending through the wall of the nozzle has in the direction at right angles to the axis of said nozzle a width approximately equal to the diameter of the nozzle, while its depth, measured parallel to the axis of the nozzle, is sutliciently small to spread out the jet of powder as a thin sheet perpendicular to the axis of the hot gas jet, which jet intercepts the said sheet over its entire Width so that the grains of powder are distributed regularly over the entire section of the jet.

This conduit may in particular be formed by a simple incision or milling formed in the nozzle at right angles to its axis.

By way of example, one embodiment of the invention is hereinafter described and illustrated in the accompanying drawing.

FIGURE 1 is a diagrammatic perspective view of the end of the projection nozzle.

FIGURE 2 is a perspective view of the powder supply device.

FIGURE 3 is an axial section of the end of a plasma I United States Patent Patented Feb. 15, 1966 projection apparatus equipped with the device according to the invention.

As shown in FIGURE 1, the nozzle 1 has in its end portion a transverse passage 2 formed by an incision, a milling or a simple saw cut at right angles to the axis of the nozzle and extending to the Vicinity of the horizontal diametrical plane of the nozzle so as to open into the duct 3 of the latter through an opening at an angle in the region of The supply tube 4 for the auxiliary gas jet containing the powder to be projected in suspension is connected to the opening 2 by means of a collar 5 of a material with a relatively low heat-conductive power, for example stainless steel, fitting over the end 1 of the nozzle, on which it may be secured by a locking screw 6.

In FIGURE 3, the collar 5 is shown in position on the external end bearing surface 1 of the nozzle of a plasma torch. The powder conduit 4 opens into the collar 5 facing the milling 2 of the nozzle, which opens into the central duct 3 of the nozzle, perpendicularly of the axis of the latter.

The nozzle is provided with an external shoulder 7 which enables the collar 5 to be secured in position with the conduit 4 just facing the milling 2 of the nozzle.

In known manner, the nozzle is extended towards the interior of the torch by a sleeve 8 surrounding the central electrode 9 and constituting the internal wall of a chamber 10 in which the cooling water for the nozzle circulates, the external Wall of this chamber being formed by the body 11 of the torch, to which the nozzle is fixed by a cap nut 12 with interposition of a packing 13.

What we claim is:

1. Apparatus for introducing materials in powder form into a projection nozzle comprising an opening through the wall of the nozzle having a width substantially equal to the diameter of the nozzle and a height less than the width, and means for supplying powder to said opening.

2. Apparatus for projecting materials in powder form into a nozzle comprising an incision in the wall of the nozzle and means for supplying powder to said incision, said incision intersecting the inner wall of the nozzle along substantially half the periphery of the cross-section of said inner wall and having a height less than the inner diameter of the nozzle.

3. An apparatus as claimed in claim 1 wherein said supplying means comprises a collar of low heat conductivity, an opening through said collar, and a tube connected to the collar.

References Cited by the Examiner UNITED STATES PATENTS 3,010,009 11/1961 Ducati 219-76 RICHARD M. WOOD, Primary Examiner. 

1. APPARATUS FOR INTRODUCING MATERIALS IN POWDER FORM INTO A PROJECTION NOZZLE COMPRISING AN OPENING THROUGH THE WALL OF THE NOZZLE HAVING A WIDTH SUBSTANTIALLY EQUAL TO THE DIAMETER OF THE NOZZLE AND A HIGHT LESS THAN THE WIDTH, AND MEANS FOR SUPPLYING POWDER TO SAID OPENING. 